Mechanical Technology

Mechanical Technology — July 2015

⎪

Hydraulic and pneumatic systems

⎪

ecognised as Eskom’s most

consistent and reliable power

station, Koeberg is the only

nuclear power station in Af-

rica. Koeberg has a pressurised water

reactor design. Featuring the largest

turbine generators in the southern

Hemisphere, Koeberg is also the most

southerly-situated nuclear power sta-

tion in the world. With international law

stipulating that all containment buildings

of all nuclear plants have to be pressure

tested every ten years, Eskom contracted

their preferred supplier, well-established

compressor and generator hire company

Rand-Air to facilitate the assignment.

Having previously supplied oil-free

compressors for the containment in-

tegrated leak rate test in 2005, the

decision to commission Rand-Air was

a result of previous successful project

partnerships with Eskom. “The purpose

of the pressure testing of the containment

building at Koeberg was to ensure that

there was no leakage which could be

harmful to the surrounding environment

Renting versus buying equipment

he dilemma of buying versus renting

machinery is a question that often

arises amongst mining and construc-

tion companies, as working to meet tight

deadlines means that project managers

are constantly seeking ways to increase

productivity.

Outsourcing equipment is beneficial

as it allows companies to focus on their

core business. Whether companies are

looking at renting short-term or long-term,

outsourcing machinery involves no major

capital outlay and companies may not have

to waste time applying for finance. Another

benefit is maintenance, because the hiring

company does it, and if any breakdowns

arise these can be quickly attended to by

replacing like-for-like hired units.

Buying machinery, on the other hand,

has appeal, as it is a once off expense and

could be considered a long-term invest-

ment. Owning the equipment also means

that the equipment forms part of the com-

pany’s assets and the company can claim

the depreciation costs. There are, however,

many challenges involved when procuring

an asset that requires continuous mainte-

nance and high upkeep costs.

Henry Fourie the business develop-

ment manager for Industrial Plant Rental

at Rand-Air, a compressor and generator

hire company, suggests that renting offers

greater benefits in the long term. “Not only

are customers guaranteed quality machines

when renting from a reputable company,

they also have peace of mind knowing that

they are paying a fully inclusive rental price

that comprises all maintenance expenses,

including; parts, labour and travelling costs

of the technician. In addition to this, the

rental option offers back up machines in

case of a breakdown to ensure that pro-

ductivity isn’t affected while the machine

is being repaired. Rental also offers an

easy upgrade or downgrade path without

additional capital outlay when compared to

outright purchases,” he argues.

Another significant factor to consider

is hiring machinery from a company that

offers 24-hour service. Industrial Plant

Rental account manager at Rand-Air, Mpho

Modjadji Ngamlane advises: “renting equip-

ment from a company that does regular

machine inspection and maintenance is

important as this minimises the chances

of breakdown, thus increasing productivity.”

An important consideration when out-

sourcing rental needs is that the hiring

of machinery is done through a company

that has experience in the rental industry.

“Rand-Air believes that exceeding customer

expectation is a significant aspect in the

service level agreement. Time is crucial

and therefore it is essential to ensure that

you are hiring from a company that makes

it their business to understand your needs

by offering the best advice and equipment,”

Fourie concludes.

An overview of the pressure-testing project recently completed with Rand Air at the Koeberg Power Station.

Inset:

Ten PTS916 Rand-Air units running through desiccant dryers pumped dry oil-free air into the con-

tainment building.

Rand-Air equipment has again

been used to successfully

complete 4.0 bar pressure

testing of the containment

building at the Koeberg Power

Station.

Successful pressure testing at Koeberg

and public,” says Andre Hopley, projects

lead technician at Rand-Air.

“Using ten PTS916 Rand-Air units

running through desiccant dryers, dry

oil-free air was pumped into the con-

tainment building. Both the inner and

the outer sector of the building were

surveyed before, during and after the

test. Water particles have a big influ-

ence on pressure testing and the end

result. We were required to match an

18 °C air temperature of the air going

into containment. We found that using

heat exchangers and chillers reduce the

pressure testing time by a few hours

allowing us to control the air pressure

distribution. The requirements for pres-

sure testing are for a dew point of -20 °C

and we managed to achieve minus -40°,”

Hopley explains.

“The pressure test took between seven

to eight hours. It took two-and-a-half

hours to reach a pressure of one bar. The

procedure stops for eight hours when it

reaches one bar, this is key in ensuring

that everything is stable enough to contin-

ue to four bar. The process requires the go

ahead from two parties namely Électricité

de France (EDF) and Eskom. It is critical

to monitor the progression thoroughly

as damage to the equipment inside the

building is potentially dangerous.

“We are proud to report that the

Rand-Air contribution to the pressure

test at Koeberg was a great success,”

concludes Hopley.